High Pressure Synthesis And Performance Optimization Of Bi_0.4Sb_1.6Te₃ Thermoelectric Material

Bi₂Te₃ based thermoelectric materials are the most commercially mature thermoelectric materials with the best performance at room temperature,However,high production cost and low thermoelectric conversion efficiency(5%?10%)limit its further application,High pressure synthesis technology has the advantages of simple process and rapid synthesis,which can effectively reduce the production cost.This paper introduces high-pressure synthesis process to prepare P-type Bi_0.4Sb_1.6Te₃ thermoelectric block material,then,Te doping and nano-SiC composite were used to optimize the thermoelectric properties of the samples.The main work and results are as follows:(1)The effect of Te-rich on the thermoelectric properties of Bi_0.4Sb_1.6Te₃ matrix in different directions was investigated.The results show that Te-rich significantly improves the Seebeck coefficient and power factor of the sample,and reduce the lattice thermal conductivity and carrier thermal conductivity of the sample,which makes the ZT of Bi_0.4Sb_1.6Te_3+x sample significantly increasing.The experimental results show that the thermoelectric properties of the samples are different in different directions,The samples obtained in the direction of vertical SPS sintering pressure have higher conductivity and power factor.At room temperature,Bi_0.4Sb_1.6Te_3.2 sample can achieve 4.89×10^-3 W/m K²,At 363K,the maximum ZT value of the sample in this direction is 1.24.The Seebeck coefficient and thermal conductivity of Bi_0.4Sb_1.6Te_3.3 sample at 403K are 223?V/K and0.87W/m K,and the maximum ZT value in this direction was 1.30.The Seebeck coefficient of samples prepared by high pressure process changes slowly with temperature,which makes average ZT value of the doped samples was maintained above 1.0 in the test temperature of 293K to 443K(150k),In the direction of parallel pressure,the average ZT value of Bi_0.4Sb_1.6Te_3.3sample is 1.23 within the temperature range,at the same time,the ZT value is always higher than 1 in the temperature range of 293K-483K(190K).(2)Bi_0.4Sb_1.6Te_3.2 sample was selected as the matrix,and nano-SiC was composite by ball milling and Spark plasma sintering to improve the thermoelectric properties of the sample.,the results show that The ball milling refined the sample grain,which hindered the precipitation of Te,The composite of nano-SiC reduces the carrier concentration and mobility of the sample,but increases the Seebeck coefficient,and the power factor of the sample remains at a high level,In addition,the presence of nano-SiC second phase and Te elemental substance significantly reduces the Carrier thermal conductivity and lattice thermal conductivity,which effectively increases the ZT value of the sample.In the end,the maximum ZT value of Bi_0.4Sb_1.6Te_3.2+0.2wt%nano-SiC was obtained at 363K is 1.2,which was 8.1%higher than that of the matrix.The average ZT value of Bi_0.4Sb_1.6Te_3.2+0.1wt%nano-SiC is 1.15 in the temperature range of 293K-443K(150K),which is 9.1%higher than that of the matrix.The power factor of Bi_0.4Sb_1.6Te_3.2+0.1wt%SiC is maintained at 4.2×10^-3 W/m K² at room temperature.